Conventionally, there is a vehicle including a pedestrian protection device for reducing an impact on a pedestrian when the pedestrian collides with the vehicle. This vehicle includes at its bumper part a collision detection device with a sensor. The vehicle is configured to, if this sensor detects a collision of a pedestrian or the like with the vehicle, activate the pedestrian protection device, mitigating an impact on the pedestrian. There is a device called a pop-up hood, for example, for this pedestrian protection device. At the time of vehicle collision detection, this pop-up hood lifts the rear end of an engine hood to increase a clearance between the pedestrian and a hard component such as an engine, and absorbs the energy of the collision with the pedestrian's head using this space to reduce the impact on the head.
The above-described collision detection device for a vehicle may be configured such that a chamber member having therein chamber space is placed on the front surface of a bumper reinforcement in the bumper of the vehicle and that the pressure in this chamber space is detected by a pressure sensor. According to the device having this configuration, if an object such as a pedestrian collides with a bumper cover, the chamber member is deformed due to a deformation of the bumper cover to make a pressure change in the chamber space. Through the detection of this pressure change by the pressure sensor, the collision detection device detects the collision of the pedestrian.
Recently, there has been proposed a tube-type collision detection device for a vehicle that detects a collision using a tube member, which is smaller in size and better in installability than the chamber-type collision detection device for a vehicle described above. This collision detection device for a vehicle is configured to include a bumper absorber that is a member for impact absorption placed in a bumper of the vehicle, a hollow tube member that is attached to the groove portion formed on the bumper absorber along the vehicle width direction, and a pressure sensor that detects a pressure in the tube member. If a pedestrian or the like collides with the vehicle front, the bumper absorber is deformed, absorbing the impact, and at the same time the tube member is also deformed. In this case, the pressure in the tube member rises, and the collision detection device detects the collision of the vehicle with the pedestrian based on the detection of this pressure change by the pressure sensor.